The invention relates to a method for manufacturing plastic components of parts mounted upon a plastic shell, using an integrated system of material handling and robots following a programmed series of operations, including spin welding and fusion welding performed by specially adapted industrial robots in work cells.
Manufacturing assembly processes are often automated with dedicated mechanical systems that are primarily arranged for a single product or very limited range of similar products. Technically advanced flexible systems are also used that utilize robots capable of being programmed and rapidly re-tooled for different operations relatively quickly compared to dedicated systems that require substantial physical rearrangement of their components.
Manufacturers are currently under increasing pressure to deliver lower volumes of manufactured components within shorter time frames. For example, many automobile manufacturers require xe2x80x9cjust in timexe2x80x9d delivery and maintain a minimal level of inventory. While these practices increase efficiency and reduce costs, they come at the expense of requiring suppliers and parts manufacturers to respond very quickly to changes in design or model type. Such practices simultaneously reduce the number of identical parts ordered in a single batch and parts manufacturers do not benefit from the long part life cycles or economies of scale that once were common. Current manufacturing procedures therefore require a high degree of flexibility to deal with relatively short runs of parts that can vary considerably from order to order.
In the present description, the example of a blow molded plastic fuel tank for automotive applications will be used as an example. It will be understood however that the method described is suitable for any plastic assembly. For example, plastic fender modules, plastic dashboard modules, plastic door panel modules, plastic roof panel modules or plastic windshield modules or for any non-automotive plastic assembly as well.
The present invention provides an integrated material handling and robotic assembly system where plastic components are assembled through a progressive series of robot work cells. By providing robotic assembly and standardized pallets conveyed on the integrated material handling system, the invention provides the advantage of a high degree of inherent flexibility as opposed to conventional hard or dedicated automation methodss.
For example, in the automotive industry, the majority of assembly line systems currently represent a hard automation system which usually does not include industrial robots, but rather is a dedicated configuration specifically designed and set up for manufacturing a specific component preferably with very limited modification or variety. The hard automation systems are relatively low cost due to the low technical sophistication required. However, a major disadvantage of such hard or dedicated automation systems is that the part life cycles of automotive components are becoming increasingly shorter and as a result, the costs of retooling and realigning such dedicated systems is becoming an increasingly important component of delivery time and of costs involved. Hard automation or dedicated lines are ideally suited for assemblies that do not change significantly over time and as a result the manufacturer can achieve the benefits of long term economies of scale. Hard or dedicated automation is tailored for low cost manufacturing of large orders over long periods of time.
High volumes of identical components result relatively low cost manufacturing and low technical sophistication is required in automating such operations. Once a dedicated line is established, maximum efficiency results from minimal modifications to the configuration during the life cycle of the specific components that are produced by the dedicated line. The more variety there is in the parts manufactured, the more effort and downtime involved in modifying the dedicated line, and efficiency decreases.
However, as mentioned above, current manufacturing and purchasing practices are much different than in the past. Volume of components ordered are relatively small, purchasers may require several manufacturers to produce the identical component in relatively small batches to increase competition, fast track production and reduce delivery time. The length of time during which a component retains its initial characteristics without any change have been drastically reduced. Numerous variations and modifications are now demanded and therefore a more flexible system of manufacturing is in demand.
It is an object of the present invention to provide an integrated system of material handling and robotic assembly to provide flexible manufacturing methods with ease of change overs between different plastic components, while providing a competitive cycle time relative to conventional dedicated assembly lines.
It is a further object of the invention to provide a high degree of accuracy and repeatability for manufacturing plastic components through the use of vision and laser scanning of parts and areas to which they are assembled.
It is a further object of the invention to optimize productivity of manufacturing plastic components utilizing robots that operate to fusion weld parts and spin weld parts in a flexible plastic component automated manufacturing system.
Further objects of the invention will be apparent from review of the disclosure, drawings and description of the invention below.
The invention provides a method robotic assembly, for manufacturing plastic components from parts mounted upon a plastic shell, using an integrated system of material handling and robots following a programmed series of operations.
Shells are progressively conveyed between a loading station and an unloading station through a number of robot work cells. The method generally includes: (1) loading and securing each shell into a fixture mounted on an associated standardized pallet at the loading station; (2) moving each loaded pallet sequentially on a conveyor to a stationary docked position at each successive robot work cell; (3) moving each loaded pallet from the docked position to the unload station; (4) determining the quality of each completed plastic component from system data accumulated from each robot cell and qualifying each completed component as good; scrap; or rework; (5) unloading each completed component from the associated pallet; and (6) conveying empty pallets to the loading station.
Further, the following cell steps are performed in one or more robot cells: (a) scanning the pallet and identifying that the pallet is locked in the proper docked position of the cell; (b) scanning an assembly area of the plastic shell and communicating location and planarity data to the associated robot of the cell; (c) selecting a plastic part from a part supply device with the robot; (d) welding the part to the assembly surface of the plastic shell using the robot to perform a spin welding or a fusion welding process. The spin welding process includes: engaging a mounting surface of the part with the assembly surface of the shell; rotating the part until the mounting and assembly surfaces are heated; and applying pressure to the part sufficient to fuse the mounting and assembly surfaces together. The fusion welding includes: simultaneously heating the mounting and assembly surfaces with heaters; and applying pressure to the part sufficient to fuse the mounting and assembly surfaces together; (e) determining the performance status of the foregoing cell steps and identifying the status as: good; scrap or rework. Good status results in conveyance of the loaded pallet for processing at any succeeding cell, but rework and scrap status result in conveyance of the loaded pallet to the unload station without processing at any succeeding cell.
As a result, a high degree of flexibility is provided in the integrated system of material handling and robotic assembly. For example, the pallets and material-handling conveyor can be reconfigured easily for any number of blow molded fuel tanks currently in existence as well as other plastic automotive assemblies such as fenders, door panels and dashboards. The standarized pallets can be readily modified with a variety of removable fixture attachments and of course the industrial robots can be readily reprogrammed for any number of operations. Retooling therefore is reduced to a minimum. Unlike a fixed configuration dedicated line, the present flexible configuration requires minimal physical modification since the robot and material handling programming accomodate the changes. Physical change over of the specialized robot end of arm tools, and possible reconfiguring of the pallet fixtures complement the reprogramming of the robot and material handling operations. In contrast, the prior art dedicated assemblies often require complete overhall and repositioning of assembly line components when different parts are to be manufactured.
The increased flexibility of integrated material handling and robotic assembly enables the manufacturer to rapidly tailor the robot assembly system for a wide variety of styles and products without changing the basic structure of the assembly system. As a result, there can be rapid change over and retooling providing significant advantage.
An advantage of the prior art dedicated line is relatively low cost due to low technical sophistication. However when a manufacturer is faced with a low volume of identical parts and high number of variations in part configurations, the low capital cost of a dedicated line is overcome by the high cost of retooling and down time during change overs to suit different styles and products. In contrast, the flexible robot assembly system with integrated material handling is relatively simple to modify for different styles and products. Highly standardized pallets, conveyors and robots enable a wide range of different styles and products to be manufactured with much less cost and downtime during any necessary retooling and reprogramming.
Further, accuracy and repeatability of manufacturing processes are increased through vision and laser scanner capabilities that locate and identify assembly areas, and adapt to accommodate relatively large tolerances when compared to a dedicated system that has limited capability to accommodate a large tolerance in the configuration of components.
Therefore, in contrast to dedicated assembly lines where it is often necessary to build an entirely new assembly line for different components or when significant changes in component design are encountered, the present invention provides an integrated material handling and robotic assembly system that in the long term provides significant capital expenditure savings due to the flexibility inherent in its technically sophisticated structure.
The integrated system combines compact and readily modified standarized pallets and industrial robot end of arm tooling that are readily changed over and reprogrammed to accomodate various components. Industrial robots can perform various operations such as cutting, spin welding, fusion or hot plate welding on a wide variety of plastic components such as blow molded fuel tanks. Industrial robots can accommodate combination tools which enable a single robot to perform multiple functions simultaneously, combined with 3-D optical vision and laser scanning systems for accurate placement and fine-tuning of part positioning. Part supply trays, bowl feeders, part magazines or dial feeding systems together with integrated palletized conveyors and controls are relatively expensive on initial capital outlay however as mentioned above the inherent flexibility provides rapid change overs in a compact system such that a wide variety of different components of various sizes are readily adapted without major modification or significant downtime.
Further advantages of the invention will be apparent from the accompanying drawings and detailed description of one example embodiment of the invention herein.